Nuclear Theory·nucl-th

Tuesday·July 6, 2021

10 papers—4 primary·6 cross-listed

01
Novel Neutron Star Structures with Nucleon Mass Radius
Wei Kou🇨🇳 · Xiaopeng Wang🇨🇳 · Xurong Chen🇨🇳
In order to reveal the difference between the latest neutron star observation experiment GW170817 and the existing theory, we mainly consider the effect of the nucleon radius on the neutron star from the existing theory. We believe that the effect of nucleon radius in neutron star is not negligible, and the mass radius of nucleon should be used instead of the charge radius. The nucleon mass radius is set as $r_{m} = 0.55 \pm 0.09$ fm from the new measurements. It is considered as an input to the "Excluded Volume Effects" model in the equation of state of nuclear matter. We propose a novel neutron star mass-radius relation by using proton mass radius is consistent with the observation GW170817.
nucl-thhep-ph0 citations
02
Electromagnetic field evolution in relativistic heavy-ion collision and its effect on flow of particles
Tewodros Gezhagn🇪🇹 · A. K. Chaubey🇪🇹
We compute the electromagnetic fields generated in relativistic heavy-ion collisions using the iEBE-VISHNU framework. We calculated the incremental drift velocity from the possible four sources of the electric force (coulomb, Lorentz, Faraday, and Plasma-based) on the particles created. The effect of this external electromagnetic field on the flow harmonics of particles was investigated, and we found out that the flow harmonics values get suppressed and rouse in a non-uniform fashion throughout the evolution. More precisely, a maximum of close to three percent increase in elliptic flow was observed. We also found mass more dominant factor than charges for the change in flow harmonics due to the created electromagnetic field. On the top of that, the magnetic field perpendicular to the reaction plane is found to be sizable while the different radial electric forces were found to cancel out each other. Finally, we found out that the inclusion of an electromagnetic field affects the flow of particles by suppressing or rising it in a non-uniform fashion throughout the evolution.
nucl-thFront.in Phys.(2022)·4 citations
03
Machine learning approach to pattern recognition in nuclear dynamics from the ab initio symmetry-adapted no-core shell model
O. M. Molchanov · K. D. Launey · A. Mercenne · G. H. Sargsyan · T. Dytrych · J. P. Draayer
A novel machine learning approach is used to provide further insight into atomic nuclei and to detect orderly patterns amidst a vast data of large-scale calculations. The method utilizes a neural network that is trained on ab initio results from the symmetry-adapted no-core shell model (SA-NCSM) for light nuclei. We show that the SA-NCSM, which expands ab initio applications up to medium-mass nuclei by using dominant symmetries of nuclear dynamics, can reach heavier nuclei when coupled with the machine learning approach. In particular, we find that a neural network trained on probability amplitudes for $s$ -and $p$ -shell nuclear wave functions not only predicts dominant configurations for heavier nuclei but in addition, when tested for the $^{20}$ Ne ground state, it accurately reproduces the probability distribution. The nonnegligible configurations predicted by the network provide an important input to the SA-NCSM for reducing ultra-large model spaces to manageable sizes that can be, in turn, utilized in SA-NCSM calculations to obtain accurate observables. The neural network is capable of describing nuclear deformation and is used to track the shape evolution along the $^{20 - 42}$ Mg isotopic chain, suggesting a shape-coexistence that is more pronounced toward the very neutron-rich isotopes. We provide first descriptions of the structure and deformation of $^{24}$ Si and $^{40}$ Mg of interest to x-ray burst nucleosynthesis, and even of the extremely heavy nuclei such as $^{166, 168}$ Er and $^{236}$ U, that build upon first principles considerations.
nucl-thPRC(2022)·17 citations
04
Cusp in the Symmetry Energy, Speed of Sound in Neutron Stars and Emergent Pseudo-Conformal Symmetry
Hyun Kyu Lee🇰🇷 · Yong-Liang Ma🇨🇳 · Won-Gi Paeng🇰🇵 · Mannque Rho🇫🇷
We review how the "cusp" predicted in the nuclear symmetry energy generated by a topology change at density $n_{1/2} \gsim 2 n_{0}$ can have a surprising consequence, so far unrecognized in nuclear physics and astrophysics communities, on the structure of dense compact-star matter. The topology change, when translated into nuclear EFT with "effective" QCD degrees of freedom in terms of hidden local and scale symmetries duly taken into account, predicts an EoS that is soft below and stiff above $n \gsim n_{1/2}$ , involving no low-order phase transitions, and yields the macrophysical properties of neutron stars consistent -- so far with no tension -- with the astrophysical observations, including the maximum mass $2.0 \lsim M / M_{⊙} \lsim 2.2$ as well as the GW data. Furthermore it describes the interior core of the massive stars populated by baryon-charge-fractionalized quasi-fermions that are neither baryonic nor quarkonic. It is argued that the cusp "buried" in the symmetry energy resulting from strong correlations with hidden heavy degrees of freedom leads, at $n \gsim n_{1/2}$ , to what we dubbed "pseudo-conformal" sound speed, $v_{p cs}^{2} / c^{2} \approx 1/3$ , precociously converged from below at $n_{1/2}$ . It is not strictly conformal since the trace of energy-momentum tensor is not zero even in the chiral limit. This observation with the topology change identified with the putative hadron-quark continuity, taking place at at density $\gsim 2 n_{0}$ , implies that the quantities accurately measured at $\sim n_{0}$ cannot give a stringent constraint for what takes place at the core density of compact stars $\sim (3 - 7) n_{0}$ . This is because the change of degrees of freedom in effective field theory is involved. We discuss the implication of this on the recent PREX-II "dilemma" in the measured skin thickness of $^{208}$ Pb.
nucl-thastro-ph.HEhep-phMod.Phys.Lett.A(2022)·36 citations
05
Gluon matter distribution in the proton and pion from extended holographic light-front QCD
Guy F. de Téramond🇨🇷 · H. G. Dosch🇩🇪 · Tianbo Liu🇨🇳 · Raza Sabbir Sufian🇺🇸 · Stanley J. Brodsky🇺🇸 · Alexandre Deur🇺🇸
The holographic light-front QCD framework provides a unified nonperturbative description of the hadron mass spectrum, form factors and quark distributions. In this article we extend holographic QCD in order to describe the gluonic distribution in both the proton and pion from the coupling of the metric fluctuations induced by the spin-two Pomeron with the energy momentum tensor in anti--de Sitter space, together with constraints imposed by the Veneziano model{\color{blue},} without additional free parameters. The gluonic and quark distributions are shown to have significantly different effective QCD scales.
↳ hep-phhep-latnucl-exnucl-thPRD(2021)·42 citations
06
Holographic Kolmogorov-Sinai entropy and the quantum Lyapunov spectrum
Georg Maier🇩🇪 · Andreas Schäfer🇩🇪 · Sebastian Waeber🇮🇱
In classical chaotic systems the entropy, averaged over initial phase space distributions, follows an universal behavior. While approaching thermal equilibrium it passes through a stage where it grows linearly, while the growth rate, the Kolmogorov-Sinai entropy, is given by the sum over all positive Lyapunov exponents. A natural question is whether a similar relation is valid for quantum systems. We argue that the Maldacena-Shenker-Stanford bound on quantum Lyapunov exponents $λ$ implies that the upper bound on the growth rate of the entropy, averaged over states in Hilbert space that evolve towards a thermal state with temperature $T$ and entropy $S_{e q}$ , should be given by $S_{e q} π T = \sum_{λ > 0} 2 π T$ . Strongly coupled, large $N$ theories with black hole duals should saturate the bound. By studying a large number of isotropization processes of random, spatially homogeneous, far from equilibrium initial states in large $N$ , $N = 4$ Super Yang Mills theory at strong coupling and computing the ensemble averaged growth rate of the dual black hole's apparent horizon area, we find both an analogous behavior as in classical chaotic systems and numerical evidence that the conjectured bound on averaged entropy growth is saturated granted that the Lyapunov exponents are degenerate $λ = \pm 2 π T$ . This fits to the behavior of classical systems with plus/minus symmetric Lyapunov spectra, a symmetry which implies the validity of Liouville's theorem.
↳ hep-thgr-qcnlin.CDnucl-thJHEP(2022)·2 citations
07
Heavy and light flavor jet quenching in different collision systems at the LHC energies
Yu-Fei Liu🇨🇳 · Wen-Jing Xing🇨🇳 · Xiang-Yu Wu🇨🇳 · Guang-You Qin🇨🇳 · Shanshan Cao🇨🇳 · Hongxi Xing🇨🇳
Recent experiments have observed large anisotropic collective flows in high multiplicity proton-lead collisions at the Large Hadron Collider (LHC), which indicates the possible formation of mini quark-gluon plasma (QGP) in small collision systems. However, no jet quenching has been confirmed in such small systems so far. To understand this intriguing result, the system size scan experiments have been proposed to bridge the gap between large and small systems. In this work, we perform a systematic study on both heavy and light flavor jet quenching in different collision systems at the LHC energies. Using our state-of-the-art jet quenching model, which combines the next-to-leading-order perturbative QCD framework, a linear Boltzmann transport model and the (3+1)-dimensional viscous hydrodynamics simulation, we provide a good description of nuclear modification factor $R_{AA}$ for charged hadrons and $D$ mesons in central and mid-central Pb+Pb and Xe+Xe collisions measured by CMS collaboration. We further predict the transverse momentum and centrality dependences of $R_{AA}$ for charged hadrons, $D$ and $B$ mesons in Pb+Pb, Xe+Xe, Ar+Ar and O+O collisions at the LHC energies. Our numerical results show a clear system size dependence for both light and heavy flavor hadron $R_{AA}$ across different collision systems. Sizable jet quenching effect is obtained for both heavy and light flavor hadrons in central O+O collisions at the LHC energies. Our study provides a significant bridge for jet quenching from large to small systems, and should be helpful for finding the smallest QGP droplet and the disappearance of QGP in relativistic nuclear collisions.
↳ hep-phnucl-exnucl-thPRC(2022)·18 citations
08
Analysis of flux-integrated semi-exclusive cross sections for charged current quasi-elastic neutrino scattering off 40Ar at energies available at the MicroBooNE experiment
A.V. Butkevich🇷🇺
Flux-integrated semi-exclusive differential and integral cross sections for quasi-elastic neutrino charged-current scattering on argon are analyzed. We calculate these cross sections using the relativistic distorted-wave impulse approximation and compare with recent MicroBooNE data. We found that the measured cross sections can be described well within the experimental uncertainties with value of the nucleon axial mass $1 < M_{A} < 1.2$ GeV. The contribution of the exclusive channel $\boldmath (ν_{μ}, μ p)$ to the flux-integrated inclusive cross sections is about 50\%.
↳ hep-phnucl-thPRC(2022)·14 citations
09
A Muon-Ion Collider at BNL: the future QCD frontier and path to a new energy frontier of $μ^{+} μ^{-}$ colliders
Darin Acosta🇺🇸 · Wei Li🇺🇸
We propose the development and construction of a novel muon-ion collider (MuIC) at Brookhaven National Laboratory (BNL) in the USA as an upgrade to succeed the electron-ion collider (EIC) that is scheduled to commence in the early 2030s, by a joint effort of the nuclear and particle physics communities. The BNL facility could accommodate a muon storage beam with an energy up to about 1~TeV with existing magnet technology. When collided with a 275~GeV hadron beam, the MuIC center-of-mass energy of about 1~TeV will extend the kinematic coverage of deep inelastic scattering physics at the EIC (with polarized beams) by more than an order of magnitude in $Q^{2}$ and $x$ , opening a new QCD frontier to address many fundamental scientific questions in nuclear and particle physics. This coverage is comparable to that of the proposed Large Hadron-Electron Collider (LHeC) at CERN, but with complementary lepton and hadron kinematics and beam polarization. Additionally, the developmentof a MuIC at BNL will focus the worldwide R\&D efforts on muon collider technology and serve as a demonstrator toward a future muon-antimuon collider at { $O$ }(10)~TeV energies, which is an attractive option to reach the next high energy frontier in particle physics at an affordable cost and a smaller footprint than a future circular hadron collider. We discuss here the possible design parameters of the MuIC, kinematic coverage, science cases, and detector design considerations including estimates of resolutions on DIS kinematic variables. A possible road map toward the future MuIC and muon-antimuon colliders is also presented.
↳ physics.acc-phhep-exhep-phnucl-ex+1Nucl.Instrum.Meth.A(2022)·34 citations
10
The anomalous $Z b b ˉ$ couplings at the HERA and EIC
Bin Yan🇺🇸 · Zhite Yu🇺🇸 · C.-P. Yuan🇺🇸
To resolve the long-standing discrepancy between the precision measurement of bottom quark forward-backward asymmetry at LEP/SLC and the Standard Model prediction, we propose a novel method to probe the $Z b b ˉ$ coupling by measuring the single-spin asymmetry $A_{e}^{b}$ of the polarized lepton cross section in neutral current DIS processes with a $b$ -tagged jet at HERA and EIC. Depending on the tagging efficiency of the final state $b$ -jet, the measurement of $A_{e}^{b}$ at HERA can already partially break the degeneracy found in the anomalous $Z b b ˉ$ coupling, as implied by the LEP and SLC precision electroweak data. In the first year run of the EIC, the measurement of $A_{e}^{b}$ can already break the degeneracy, due to its much larger luminosity and higher electron beam polarization. With enough integrated luminosity collected at the EIC, it is possible to either verify or exclude the LEP data and resolve the $A_{FB}^{b}$ puzzle. We also discuss the complementary roles between the proposed $A_{e}^{b}$ measurement at EIC and the measurement of $g g \to Z h$ cross section at the HL-LHC in constraining the anomalous $Z b b ˉ$ coupling.
↳ hep-phhep-exnucl-exnucl-thPLB(2021)·33 citations

Affiliations

first authorsco-authorsvia INSPIRE